This invention concerns the synthesis of chlorolactones from unsaturated carboxylic acids.
The resultant chlorolactones may be used generally as intermediary synthesis products in organic chemistry or, more particularly in so far as regards .gamma.-chloromethyl .gamma.-butyrolactone or .delta.-chloromethyl .delta.-valerolactone, as solvents, for example for acetylene, for epoxy resins, for polyvinyl chloride and its copolymers or still for other resins.
The halolactonization reaction is known since the beginning of the century and is still of interest in synthetic organic chemistry. See for example M. D. DOWLE and D. I. DAVIES, Chem. Soc. Rev., 8 (2), 171 (1979).
Whereas the bromo-and iodolactones obtained by reacting halogen, in basic medium, on an unsaturated acid according to the scheme below, have been largely described, no example is known of a direct and selective conversion of unsaturated acids to chlorolactones in an economical way; the lactonization reaction is, as a matter of fact, in competition with the dichlorination reaction as indicated in the following references: E. E. VAN TAMELEN & M. SHAMMA, J. Am. Chem. Soc., 76, 2315 (1954); G. BERTI, Gazzeta, 81, 305 (1951); G. BERTI, Tetrahedron, 4, 393 (1958); W. REPPE, O. SCHLICHLING, K. KLAGER & T. TOEPEL, Annalen, 560, 1 (1948); R. ODA, S. MUNEIMIYA & M. OKANO, J. Org. Chem., 26 (5), 1341 (1961); G. F. BLOOMFIELD & E. H. FARMER, J. Chem. Soc., 2062 (1932); and U.S. Pat. No. 4,031,115. ##STR2## In these formulae, X is a halogen atom and n is an integer, for example from 1 to 12.
B. DAMIN, J. GARAPON and B. SILLION, Tetr. Letters 21, 1709 (1980), have recently described a chloroxy-carboxylation of olefins by reaction of "T chloramine" (sodium N-chloro-para- toluenesulfonamidate) in the presence of a carboxylic acid, according to the following scheme: ##STR3## wherein each of R and R' represents a hydrogen atom or an aromatic or aliphatic hydrocarbon radical having from 1 to 8 carbon atoms and R" is an aliphatic radical having from 1 to 5 carbon atoms.
However, as is apparent from the reaction scheme, the chloroxycarboxylation reaction is accompanied by the formation of a chlorotosylation product (II) with yields which may reach 15%.
It has now been discovered that it is possible to form chlorolactones with high yields and without secondary chlorotosylation or dichlorination reactions.